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Mill is a waste prevention technology company reimagining what it means to eliminate waste, starting with food. We build smart systems and infrastructure for homes, businesses, and municipalities that transform food scraps from landfill-bound waste into valuable resources, including chicken feed. Tens of thousands of Mill’s residential food recyclers are already helping households divert millions of pounds of food scraps every year, paving the way for our upcoming launch of Mill Commercial—the industry’s first end-to-end solution for managing, understanding, and preventing food waste in commercial environments (e.g. grocery, restaurants, food services). At Mill, we are passionate about building easy-to-use, beautifully designed technologies that keep food in the food system and out of landfills.
We're looking for a Hardware-in-the-Loop (HIL) Test Engineer to own the test station for Mill Commercial's program including hardware, sensor and actuator emulation, and plant models: systems to emulate include safety interlocks, load cells, motor feedback, thermocouples, and heater elements.
This is a hands-on, build-and-maintain role. You'll take the station from vendor commissioning to a working bench, then keep extending it: adding channels and fault-injection paths, writing and tweaking the thermal and torque plant models in Simulink, and turning engineering requirements into automated tests that run in CI. You'll work day to day with Firmware, Systems, Test Engineering and EE, and you'll be the person who knows why a test passed or failed at the signal level.
What You'll Do- Own the HIL test station end to end: rig hardware, I/O and emulation modules, wiring and harnessing to the DUT, power and reset control, and the bench equipment around it
- Lead vendor commissioning and bring-up, then take over the station as the in-house owner once the vendor hands off
- Build and maintain plant models in Simulink (oil jacket thermal, air heater and airflow, vessel cool-down, grinder load torque) and keep them correlated against real-device data
- Extend the rig to cover new tests: add emulation channels, fault-injection paths (thermocouple open/short/drift, disconnected interlock lines, degraded tach signals) and timing capture as the test plan grows.
- Translate engineering and safety requirements into automated HIL test cases with programmatic pass/fail, and integrate them into the Linux-based CI regression
- Debug failures to root cause across the rig, the plant model and the firmware, working with Firmware and EE to tell a real defect from a test-infrastructure issue
- Keep the station reliable: calibration, spares, documentation, and a known-good configuration that other engineers can run tests on without you
- Partner with SW QA to define test plan based on product requirements and ensure the station can test all cases
- Partner with Systems and Test Engineering on the boundary between HIL coverage, bare-board tests and full-system tests
- 4+ years in test, controls or systems engineering on electromechanical products, with at least 2 years hands-on with HIL or real-time simulation rigs
- Strong Simulink and MATLAB: you've built and tuned plant models (thermal, mechanical or electrical) and deployed them to a real-time target
- Able to read and trace C code: you can follow firmware control logic well enough to understand what a test is exercising and where a failure originates
- Comfortable with signal-level work: thermocouples, strain gauges, hall-effect and discrete inputs, PWM drive lines, and the I/O modules that emulate them
- Practical bench skills: wiring, harness build, oscilloscope and DMM work
- Strong documentation and organization skills
- Experience with test automation: scripting test sequences, programmatic pass/fail, results logging, and integrating into a regression pipeline
- Clear, direct communicator: you write test cases others can run and you explain rig behavior to firmware engineers in their terms
- Hands-on experience with Speedgoat, dSPACE, NI VeriStand or similar HIL hardware, including Simulink Real-Time or an equivalent toolchain
- Experience working with Linux-based embedded systems (Jetson, Yocto or Debian-class targets) and Linux CI tooling
- Familiarity with standard automation APIs such as ASAM XIL, or with Python-based test frameworks and MQTT
- Background in safety and interlock testing, fault injection, or functional-safety test methods
- Experience with thermal or motor-drive systems: heaters, PID loops, DC motor torque and current limiting
- Experience at an early-stage hardware startup, where you set up the process rather than inherit it
The estimated base salary range for this position is $165K to $185K, which does not include the value of benefits or a potential equity grant. A wide range of factors are considered in making compensation decisions, including but not limited to skill sets, market conditions, experience and training, licensure and certifications, and business and organizational needs.
Skills Required
- 4+ years of experience in test, controls, or systems engineering on electromechanical products
- At least 2 years of hands-on experience with HIL or real-time simulation rigs
- Strong MATLAB and Simulink experience building, tuning, and deploying plant models to real-time targets
- Ability to read and trace C code
- Experience with thermocouples, strain gauges, Hall-effect sensors, discrete inputs, PWM drive lines, and emulated I/O modules
- Practical bench skills including wiring, harness building, oscilloscope use, and DMM work
- Experience with test automation, scripting test sequences, programmatic pass/fail, results logging, and regression pipeline integration
- Strong documentation and organizational skills
- Clear written and verbal communication skills
- Experience with Speedgoat, dSPACE, NI VeriStand, or similar HIL hardware
- Experience with Simulink Real-Time or an equivalent toolchain
- Experience with Linux-based embedded systems and Linux CI tooling
- Familiarity with ASAM XIL, Python-based test frameworks, or MQTT
- Background in safety and interlock testing, fault injection, or functional-safety test methods
- Experience with thermal or motor-drive systems, including heaters, PID loops, DC motor torque, and current limiting
- Experience working at an early-stage hardware startup
Mill Compensation & Benefits Highlights
The following summarizes recurring compensation and benefits themes identified from responses generated by popular LLMs to common candidate questions about Mill and has not been reviewed or approved by Mill.
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Fair & Transparent Compensation — Pay is positioned as competitive for several senior technical and business roles, supported by multiple six‑figure base ranges in recent postings. Total compensation snapshots commonly cluster in the mid‑ to high‑$100Ks for individual‑contributor roles, reinforcing a generally market-competitive posture for the Bay Area.
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Leave & Time Off Breadth — Time-off coverage appears broad, including paid holidays, paid sick days, flexible time off, and an unlimited vacation policy, with some company-wide time off. The overall setup signals strong flexibility for managing personal time, though day-to-day use may depend on team norms.
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Healthcare Strength — Core health coverage is described as comprehensive, including medical, dental, and vision, alongside wellness programs and an FSA. The package breadth suggests a solid baseline consistent with tech-startup standards.
Mill Insights
What We Do
We’re on a mission to eliminate waste for good, starting with the food that ends up in landfills. Did you know that more than half of the food in landfills comes from home kitchens (ReFED)? And food in landfills turns into methane – which is 80x more potent than CO2 over a 20-year period (IPCC). At Mill, we’re working to turn kitchen scraps into food for chickens. This keeps food in our food system and out of landfills.
Why Work With Us
Food isn't trash. Mill keeps it from stinking up your kitchen – and the planet.
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